The present invention relates generally to a cutting device and, more particularly, to a cutting device utilizing an annular blade with an internal cutting edge used primarily for slicing thin wafers from ceramic materials.
Internal diameter cutting devices are widely employed for slicing thin crystal wafers used in the production of semiconductors. The annular cutting blades (ID discs) or discs utilized with such machines have circular cutting edges on their internal peripheries, usually in the form of a coating having diamond dust suspended therein. These cutting discs generally are clamped between a pair of annular clamping rings that are then secured to a rotatable spindle. To facilitate this operation the blades normally are provided with a plurality of annularly distributed mounting holes that accommodate mounting screws.
The operation of centering and tensioning an ID disc requires a considerable degree of care and skill, and as a cutting machine may require several replacements of worn-out wheels in the course of a day, the time lost in properly centering and tensioning the wheels within the holding ring and mounting the same on the spindle is very considerable. Thus, in one method of preparing a tensioned ID disc assembly, there are employed two steel rings, one of which has a convex and the other a concave surface, between which the wheel is clamped in such manner that a radial tension is created therein. To effect the assembly, the convex ring is first placed upon a centering fixture which includes an annular base shoulder and a centrally disposed and axially movable centering sleeve which consists essentially of a cone-shaped member and a knurled knob for rotating it counter-clockwise or clockwise to raise or lower the cone member. The ring with the convex surface is first placed over the base shoulder and the cutting wheel is then placed in position over the centering sleeve with its peripheral region over the convex area of the ring. The centering sleeve knob is then turned counter-clockwise until the sleeve touches the cutting edge of the wheel. A hold-down plate is now placed over the sleeve and upon the wheel, and is centered as closely as possible. The centering sleeve is then turned counterclockwise until the sleeve meets resistance, and tends to turn the hold-down plate and cutting wheel, the wheel being now in centered position. The outside or concave ring is now placed upon the convex ring, while the hold-down plate is held by holddown clamps to lock the hold-down plate and cutting wheel in place.
The second ring is then rotated until screw holes therein are brought into registry with threaded holes in the convex ring. Clamping screws are then inserted into the screw holes and tightened to apply tension to the cutting wheel as the two rings are forced together. The clamps are then released and the hold-down plate is removed. The assembly is now rotated off the centering sleeve and base shoulder, and is then mounted on the spindle.
In another known method of centering and tensioning an ID disc between a pair of clamping steel rings there is again employed a centering device which includes a cone-shaped member, and also three centering chuck jaws. The centering device includes a ring provided with dowel pins by means of which a first clamping ring with flat surfaces is positioned on the centering device. The clamping face of the ring is provided with knurls and a V-groove designed to grip the peripheral region of the cutting wheel.
After placing the ID disc upon the first ring, the chuck jaws are expanded against the inside periphery of the wheel and thereby center it. The wheel and chuck are then rotated to effect matching of cap screw-holes in the first ring and wheel. A second or lock ring is then positioned over the wheel, such ring being provided with a V-rib which mates with the V-groove in the first ring. Cap screws are then applied to bind the two rings with the wheel there between for providing an initial tensioning.
The second ring is internally threaded, and there is then screwed into such ring an externally threaded tensioning ring, which is turned until it bears against the surface of the cutting wheel. Further rotation of the tensioning ring, as with a spanner wrench, develops radial tension in the cutting wheel. The assembly is then mounted on the cutting machine.
It will be evident from the foregoing description that the accurate centering and tensioning of ID discs on a machine is a delicate and time-consuming operation. The object of this invention, therefore, is to provide a cutting machine on which annular ID discs can be accurately mounted in less time than has been required previously.